1. Field of the Invention
The present invention relates to the railroad signaling, and in particular to an apparatus and method for vitally monitoring and determining the state of wayside signaling equipment.
2. Description of the Related Art
Railroad systems include various types of wayside equipment which is located at geographically dispersed positions along the track. Such wayside equipment includes wayside signaling equipment, including signal lamps, switches and hazard detectors, which communicate track information, such as right-of-way information, speed restrictions, and track condition information, to trains traveling along the track.
Positive train control (PTC) refers to various technologies that are used to monitor and control the movements of trains to provide increased safety. A typical PTC system consists of a centralized control center, an on-board computer provided on the train, various types of wayside equipment as just described, and a wireless communication system that allows for wireless communications between the elements just identified. More specifically, such PTC systems typically employ an overlay system wherein each piece of wayside equipment is operatively coupled to a wayside interface device that monitors the status of wayside equipment in a fail safe manner and wirelessly transmits the status to the on-board computer of each oncoming train. For example, a wayside interface device may be coupled to a signal lamp (having individual red, yellow and green lamps) for monitoring and reporting the aspect of the signal lamp to oncoming trains. In PTC systems, it is important that wayside interface devices not falsely interpret and broadcast the state of the associated wayside signaling equipment in a more permissive manner. In other words, if such wayside interface device are going to fail, they should fail into a safe (less permissive) mode for the train.
While many known PTC systems employing an overlay system as just described have proven to be effective in certain situations, there is room for improvement in the field of positive train control, and in particular as it relates to monitoring and determining the state of wayside signaling equipment.